More than 224,000 people are expected to be diagnosed with lung cancer alone in the U.S. in 20151. With 159,000 deaths expected to result from these new cases, it is the most lethal cancer today. Detecting and treating these patients in early stages of this disease offers the best chance of cure. Stereotactic ablative radiotherapy (SABR) is a new technology for delivering very high radiation dose to a small tumor target volume with high precision. The clinical results from SABR of early lung cancers are very promising with outcome matching that from surgery for both operable and inoperable patients2,3. Conducting SABR treatments, however, is tedious and time-consuming, largely due to the need to verify the target position throughout the duration of the treatment. Development of new technologies that can provide rapid and accurate patient verification images is important to the success of SABR program. This is of particular importance given that the number of lung cancers is likely to rise due to an aging population and the success of low-dose CT screening4,5.